Replacing heart valves with prosthetic valves was, until recently, a complicated surgical procedure that involved cutting open the chest, establishing blood flow through a blood pump, stopping the heart, etc. This complicated procedure, even when performed perfectly, required extensive recovery time due to the invasiveness and damage done to access the implantation site. Additionally, the risk of infection or other complications is extremely high.
Numerous advancements have been made to develop prosthetic valves that can be implanted percutaneously, using a catheter to snake the prosthetic valve through the vasculature to the implantation site. If successful, the recovery time is greatly minimized relative to conventional open-heart surgery.
A designer of a percutaneously-delivered prosthetic valve is faced with numerous challenges, however. First and foremost is designing a prosthetic valve that can be compressed enough to be inserted into a catheter small enough to be navigated to the valve site through the vasculature. Other challenges include anchoring the valve at the valve site so the valve does not migrate after release; including a support structure for the valve that is robust enough to push the native, often calcified valve out of the way and prevent it from later interfering with the function of the new valve; ensuring that the new valve allows proper flow in a desired direction and effectively stops flow in the opposite direction; ensuring that no blood flows around the sides of the implanted device (this is known as perivalvular leakage); designing a prosthetic valve device that does not fail due to fatigue after hundreds of thousands of cycles of leaflet function; designing a valve that meets all of these criteria and can still be manufactured economically; and the list goes on.
These prosthetic valves, and their respective delivery catheters, are designed to replace a particular native valve, such as the aortic valve, for example. Percutaneous navigation to a valve is easiest, and least traumatic to the patient, when a smaller catheter is used. Smaller catheters, however, present challenges when designing effective prosthetic valves that can be compressed enough to fit, and slide, within the lumen of a small catheter, such as a 16 Fr or even a 14 Fr catheter. Significant strides have been made in recent years in designing prosthetic valves that have reduced profiles when in a catheter-loaded configuration. For example, the devices described in U.S. Patent Publication Number 2006/0271166 to Thill et al., the contents of which are incorporated by reference herein, can assume an elongated, unfolded configuration when loaded into a catheter and, when released from the catheter at a target site, resume a folded configuration. The present invention is directed to taking this innovative concept and presenting additional ways that the loaded configuration could present an even lower profile.